U.S. patent application number 11/068246 was filed with the patent office on 2006-04-20 for pigment dispersions that exhibit variable particle size or variable viscosity.
Invention is credited to Howard A. Doumaux, Anne M. Kelly-Rowley, David Tyvoll, Sundar Vasudevan.
Application Number | 20060084720 11/068246 |
Document ID | / |
Family ID | 35385051 |
Filed Date | 2006-04-20 |
United States Patent
Application |
20060084720 |
Kind Code |
A1 |
Tyvoll; David ; et
al. |
April 20, 2006 |
Pigment dispersions that exhibit variable particle size or variable
viscosity
Abstract
An inkjet ink including a polymer-attached pigment formulated to
exhibit a compact configuration and an elongated configuration,
which provides the polymer-attached pigment with a variable
particle size. The polymer-attached pigment may include a pigment
having at least one polymer attached to its surface. The at least
one polymer may be formed from a hydrophobic segment and a
hydrophilic segment, where the hydrophilic segment is soluble in an
aqueous environment and the hydrophobic segment is insoluble in the
aqueous environment. The polymer-attached pigment may be dispersed
in an ink vehicle to provide a low viscosity inkjet ink. The inkjet
ink may optionally include at least one binder formed from a
hydrophobic segment and two hydrophilic segments. A method of
producing a printed image having good durability and gloss is also
disclosed.
Inventors: |
Tyvoll; David; (La Jolla,
CA) ; Doumaux; Howard A.; (San Diego, CA) ;
Kelly-Rowley; Anne M.; (San Diego, CA) ; Vasudevan;
Sundar; (Corvallis, OR) |
Correspondence
Address: |
HEWLETT PACKARD COMPANY
P O BOX 272400, 3404 E. HARMONY ROAD
INTELLECTUAL PROPERTY ADMINISTRATION
FORT COLLINS
CO
80527-2400
US
|
Family ID: |
35385051 |
Appl. No.: |
11/068246 |
Filed: |
February 28, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60620527 |
Oct 19, 2004 |
|
|
|
Current U.S.
Class: |
523/160 ;
523/161 |
Current CPC
Class: |
C09C 3/10 20130101; B41M
7/00 20130101; C09C 1/56 20130101; C01P 2006/22 20130101; C09D
11/322 20130101 |
Class at
Publication: |
523/160 ;
523/161 |
International
Class: |
C03C 17/00 20060101
C03C017/00; C09D 11/00 20060101 C09D011/00 |
Claims
1. An inkjet ink, comprising: a polymer-attached pigment dispersed
in an ink vehicle, the polymer-attached pigment comprising at least
one polymer attached to a surface of a pigment, wherein at least a
first portion of the at least one polymer is soluble in an organic
solvent and at least a second portion of the at least one polymer
is insoluble in the organic solvent.
2. The inkjet ink of claim 1, wherein the at least a first portion
of the at least one polymer is soluble in an aqueous environment
and the at least a second portion of the at least one polymer is
insoluble in the aqueous environment.
3. The inkjet ink of claim 1, wherein the pigment is a carbon black
or an organic pigment.
4. The inkjet ink of claim 1, wherein the polymer-attached pigment
is present in the inkjet ink in an amount ranging from
approximately 0.25% by weight of a total weight of the inkjet ink
to approximately 15% by weight of a total weight of the inkjet
ink.
5. The inkjet ink of claim 1, wherein the at least one polymer has
a molecular weight ranging from approximately 1500 to less than
approximately 50,000.
6. The inkjet ink of claim 1, wherein the at least one polymer is
covalently bonded to from approximately 10% to approximately 70% of
a surface area of the pigment.
7. The inkjet ink of claim 1, wherein the at least one polymer
comprises at least one hydrophilic segment selected from the group
consisting of an acrylic acid, a methacrylic acid, an acrylamide,
styrene-4-sulfonic acid, 4-vinylbenzoic acid, and alkylene oxide
adducts of acrylic acid or methacrylic acid.
8. The inkjet ink of claim 1, wherein the at least one polymer
comprises at least one hydrophobic segment selected from the group
consisting of a styrene, an alkyl styrene, a phenoxyethylacrylate,
an alkyl or aryl acrylate, an alkyl or aryl methacrylate, and a
benzylmethacrylate and at least one hydrophilic segment.
9. The inkjet ink of claim 1, wherein the organic solvent comprises
1,2-hexanediol, ethylene glycol monophenyl ether, or mixtures
thereof.
10. The inkjet ink of claim 1, wherein the organic solvent
comprises an organic solvent having a boiling point higher than a
boiling point of water.
11. The inkjet ink of claim 1, wherein the polymer-attached pigment
is homogenously dispersed in the inkjet ink.
12. The inkjet ink of claim 1, wherein the polymer-attached pigment
is formulated to exhibit a compact configuration in an aqueous
environment.
13. The inkjet ink of claim 1, wherein the polymer-attached pigment
has an average particle size ranging from approximately 1 nm to
approximately 300 nm in the compact configuration.
14. The inkjet ink of claim 1, wherein the polymer-attached pigment
is formulated to exhibit an elongated configuration in an
organic-enriched environment.
15. The inkjet ink of claim 1, wherein the polymer-attached pigment
is formulated to have an average particle size in the elongated
configuration that is from approximately 5% to approximately 25%
larger than the average particle size in the compact
configuration.
16. The inkjet ink of claim 1, wherein the polymer-attached pigment
is formulated to have a variable particle size and a variable
viscosity.
17. The inkjet ink of claim 1, further comprising at least one
polymeric binder comprising a hydrophobic segment and two
hydrophilic segments.
18. The inkjet ink of claim 17, wherein the hydrophobic segment is
selected from the group consisting of a styrene, an alkyl styrene,
a phenoxyethylacrylate, an alkyl or aryl acrylate, an alkyl or aryl
methacrylate, and a benzylmethacrylate.
19. The inkjet ink of claim 17, wherein each of the two hydrophilic
segments is independently selected from the group consisting of an
acrylic acid, a methacrylic acid, an acrylamide, styrene-4-sulfonic
acid, 4-vinylbenzoic acid, and alkylene oxide adducts of acrylic
acid or methacrylic acid.
20. An inkjet ink, comprising: a polymer-attached pigment dispersed
in an ink vehicle, the polymer-attached pigment comprising at least
one hydrophobic segment and at least one hydrophilic segment
attached to a surface of a pigment, wherein the at least one
hydrophobic segment is soluble in an organic solvent of the ink
vehicle and the at least one hydrophilic segment is insoluble in
the organic solvent.
21. The inkjet ink of claim 20, wherein the at least one
hydrophobic segment is attached to the pigment and the at least one
hydrophilic segment is attached to the at least one hydrophobic
segment.
22. The inkjet ink of claim 20, wherein the at least one
hydrophilic segment is soluble in an aqueous environment and the at
least one hydrophobic segment is insoluble in the aqueous
environment.
23. The inkjet ink of claim 20, further comprising at least one
polymeric binder comprising a hydrophobic segment and two
hydrophilic segments.
24. The inkjet ink of claim 23, wherein the hydrophobic segment is
selected from the group consisting of a styrene, an alkyl styrene,
a phenoxyethylacrylate, an alkyl or aryl acrylate, an alkyl or aryl
methacrylate, and a benzylmethacrylate.
25. The inkjet ink of claim 23, wherein each of the two hydrophilic
segments is independently selected from the group consisting of an
acrylic acid, a methacrylic acid, an acrylamide, styrene-4-sulfonic
acid, 4-vinylbenzoic acid, and alkylene oxide adducts of acrylic
acid or methacrylic acid.
26. A method of printing an image having good durability and gloss,
comprising: providing an inkjet ink comprising at least one
polymer-attached pigment, the polymer-attached pigment formulated
to exhibit a compact configuration and an elongated configuration,
wherein at least a first portion of the at least one polymer is
soluble in an organic solvent and at least a second portion of the
at least one polymer is insoluble in the organic solvent;
depositing the inkjet ink on a print medium; and subjecting the
inkjet ink to an organic-enriched environment.
27. The method of claim 26, wherein providing an inkjet ink
comprising at least one polymer-attached pigment comprises
providing an inkjet ink comprising at least one polymer covalently
bonded to a surface of the pigment.
28. The method of claim 26, wherein providing an inkjet ink
comprising at least one polymer-attached pigment comprises
providing an inkjet ink comprising at least one polymer attached to
a surface of the pigment.
29. The method of claim 28, wherein providing an inkjet ink
comprising at least one polymer attached to a surface of the
pigment comprises providing at least one polymer comprising at
least one hydrophobic segment and at least one hydrophilic
segment.
30. The method of claim 28, wherein providing an inkjet ink
comprising at least one polymer attached to a surface of the
pigment comprises providing at least one hydrophobic segment and at
least one hydrophilic segment selected from the group consisting of
an acrylic acid, a methacrylic acid, an acrylamide,
styrene-4-sulfonic acid, 4-vinylbenzoic acid, and alkylene oxide
adducts of acrylic acid or methacrylic acid.
31. The method of claim 28, wherein providing an inkjet ink
comprising at least one polymer attached to a surface of the
pigment comprises providing at least one hydrophobic segment
selected from the group consisting of styrene, an alkyl styrene, a
phenoxyethylacrylate, an alkyl or aryl acrylate, an alkyl or aryl
methacrylate, and a benzylmethacrylate and at least one hydrophilic
segment.
32. The method of claim 28, wherein providing an inkjet ink
comprising at least one polymer attached to a surface of the
pigment comprises providing an inkjet ink comprising at least one
hydrophobic segment attached to the surface of the pigment and at
least one hydrophilic segment attached to the at least one
hydrophobic segment.
33. The method of claim 26, wherein providing an inkjet ink
comprising at least one polymer-attached pigment comprises
providing the at least one polymer-attached pigment in the compact
configuration.
34. The method of claim 26, wherein providing an inkjet ink
comprising at least one polymer-attached pigment comprises
providing at least one polymer-attached pigment having a particle
size ranging from approximately 1 nm to approximately 300 nm.
35. The method of claim 26, further comprising adding at least one
polymeric binder comprising a hydrophobic segment and two
hydrophilic segments to the inkjet ink.
36. The method ink of claim 35, wherein the hydrophobic segment is
selected from the group consisting of a styrene, an alkyl styrene,
a phenoxyethylacrylate, an alkyl or aryl acrylate, an alkyl or aryl
methacrylate, and a benzylmethacrylate.
37. The method of claim 35, wherein each of the two hydrophilic
segments is independently selected from the group consisting of an
acrylic acid, a methacrylic acid, an acrylamide, styrene-4-sulfonic
acid, 4-vinylbenzoic acid, and alkylene oxide adducts of acrylic
acid or methacrylic acid.
38. The method of claim 26, wherein subjecting the inkjet ink to an
organic-enriched environment comprises converting a compact
configuration of the polymer-attached pigment to an elongated
configuration.
39. The method of claim 26, wherein subjecting the inkjet ink to an
organic-enriched environment comprises increasing an average
particle size of the polymer-attached pigment by from approximately
5% to approximately 25% relative to the average particle size of
the polymer-attached pigment in the compact configuration.
40. The method of claim 26, wherein subjecting the inkjet ink to an
organic-enriched environment comprises solubilizing the at least
one hydrophobic segment in the organic-enriched environment.
41. The method of claim 26, wherein subjecting the inkjet ink to an
organic-enriched environment comprises increasing a concentration
of an organic solvent in the inkjet ink.
42. The method of claim 26, wherein subjecting the inkjet ink to an
organic-enriched environment comprises removing at least a portion
of water from the inkjet ink.
43. The method of claim 26, wherein subjecting the inkjet ink to an
organic-enriched environment comprises entangling the at least one
polymer to form a film.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. provisional
patent application Ser. No. 60/620,527, filed Oct. 19, 2004.
FIELD OF THE INVENTION
[0002] The present invention relates to a pigment dispersion for
use in an inkjet ink and, more specifically, to a pigment
dispersion having a variable particle size or variable
viscosity.
BACKGROUND OF THE INVENTION
[0003] Inkjet printing is a nonimpact process of printing text or
images by depositing inkjet ink on a print medium. The inkjet ink
includes an aqueous-based ink vehicle and a colorant, such as a dye
or a pigment. Dyes are more commonly used in inkjet inks because
dyes are easily dissolved or solvated in the ink vehicle. However,
images printed with dye-based inkjet inks are generally less
waterfast, lightfast, and resistant to ozone.
[0004] In contrast, pigment-based inkjet inks provide printed
images having improved waterfastness and lightfastness. While
pigment-based inkjet inks have these desirable properties, the
pigments are typically insoluble in the ink vehicle. The pigments
form discrete particles that clump or agglomerate if they are not
stabilized in the inkjet ink. To prevent the pigments from
agglomerating or settling out of the ink vehicle, the pigments are
uniformly dispersed in the inkjet ink and stabilized in the
dispersed form until the inkjet ink is used for printing.
[0005] To form stable pigment dispersions, dispersants or
surfactants are added to the ink vehicle. The dispersant is
typically a polymer formed by polymerizing hydrophobic monomers,
hydrophilic monomers, hydrophobic copolymers, and/or hydrophilic
copolymers. The dispersant binds to a surface of the pigment,
providing stability to the pigment dispersion. When printing is
desired, the pigment is precipitated from the inkjet ink and onto
the print medium by solvent evaporation. This process is enhanced
by the presence of salts, acids, or polymers in the print medium.
Inks that contain dispersants provide printed images with good
durability and gloss. However, a large amount of the dispersant is
needed to produce these desirable properties, which increases the
viscosity of the inkjet ink prohibitively. This increase in
viscosity reduces the usefulness of dispersants in inkjet inks
because it affects the firing reliability and print quality of
inkjet pens.
[0006] Alternatively, the pigment is stably dispersed in the inkjet
ink by modifying the surface of the pigment to include covalent
attachment of polymeric or organic groups. The surface-modified
pigments are referred to in the art as "self-dispersed pigments" or
"polymer-attached pigments." Using surface-modified pigments
improves the formulation latitude of the inkjet ink and reduces the
viscosity of the inkjet ink compared to the viscosity of inkjet
inks that have dispersants. However, if the inkjet ink includes
unbound polymeric or organic groups, these still undesirably
contribute to, and increase, the viscosity of the inkjet ink.
[0007] It would be desirable to provide an inkjet ink that produces
printed images that have good gloss and durability without
increasing the viscosity of the inkjet ink.
BRIEF SUMMARY OF THE INVENTION
[0008] The present invention relates to an inkjet ink having a
polymer-attached pigment that is dispersed in an ink vehicle. The
polymer-attached pigment includes at least one polymer attached to
a surface of a pigment. The at least one polymer may include at
least one hydrophobic segment and at least one hydrophilic segment.
The at least one hydrophobic segment may be attached to the pigment
and the at least one hydrophilic segment may be attached to the
hydrophobic segment. The inkjet ink may optionally include at least
one binder formed from a hydrophobic segment and two hydrophilic
segments.
[0009] The present invention also relates to a method of forming a
printed image having improved gloss and durability. The method
includes providing an inkjet ink having at least one
polymer-attached pigment that is formulated to exhibit a compact
configuration and an elongated configuration. The polymer-attached
pigment includes at least one polymer attached to a surface of a
pigment.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0010] While the specification concludes with claims particularly
pointing out and distinctly claiming that which is regarded as the
present invention, the advantages of this invention can be more
readily ascertained from the following description of the invention
when read in conjunction with the accompanying drawings in
which:
[0011] FIGS. 1-3 schematically illustrate an embodiment of a
polymer-attached pigment of the present invention in a compact
configuration;
[0012] FIGS. 4-6 schematically illustrate an embodiment of a
polymer-attached pigment of the present invention in an elongated
configuration;
[0013] FIG. 7 schematically illustrates an embodiment of a binder
and a polymer-attached pigment of the present invention in a
compact configuration; and
[0014] FIG. 8 schematically illustrates an embodiment of a binder
and a polymer-attached pigment of the present invention in an
elongated configuration.
DETAILED DESCRIPTION OF THE INVENTION
[0015] A polymer-attached pigment formulated to exhibit a compact
configuration and an elongated configuration is provided. The
polymer-attached pigment exhibits the compact configuration or the
elongated configuration depending on an environment to which the
polymer-attached pigment is exposed. The polymer-attached pigment
may be dispersed in an ink vehicle to provide a low viscosity
inkjet ink. The polymer-attached pigment may include a pigment
having at least one polymer attached to its surface. A first
portion of the polymer may be soluble in an aqueous environment and
a second portion of the polymer may be insoluble in the aqueous
environment. The polymer-attached pigment may adopt the compact
configuration when the polymer-attach pigment is exposed to the
aqueous environment or may adopt the elongated configuration when
the polymer-attached pigment is exposed to an organic-enriched
environment.
[0016] The pigment used in the inkjet ink may be a conventional
pigment for use in inkjet printing, such as carbon black, an
organic pigment, a white inorganic pigment, or a colored inorganic
pigment. The pigment may be a black pigment or a colored pigment,
such as a blue, black, brown, cyan, green, white, violet, magenta,
red, or yellow pigment. In addition, mixtures of colored pigments
may be used in the inkjet ink, as well as mixtures of black and
colored pigments. The inorganic pigment may include, but is not
limited to, iron oxides, titanium oxides, zinc oxide, zinc
sulphides, zinc chromate, zirconium oxide, iron blue, ultramarine
blue, chromium oxide, ultramarine, cobalt blue, cobalt violet,
silicon dioxide, nickel oxides, aluminium oxides, ferric
ferrocyanide (Prussian blue), lead chromate, white lead, basic lead
sulfate, cadmium yellow, chrome yellow, barium sulfate, calcium
carbonate, calcium silicate, and manganese violet. In one
particular embodiment, the pigment is a carbon black or an organic
pigment.
[0017] The pigment may be a carbon black pigment, such as a channel
black, a furnace black, or a lamp black. Examples of carbon blacks
include those sold under the Regal.RTM., Black Pearls.RTM.,
Elftex.RTM., Monarch.RTM., Mogul.RTM., and Vulcan.RTM. trademarks,
which are available from Cabot Corporation (Boston, Mass.). The
carbon black may include, but is not limited to, Black Pearls.RTM.
2000, Black Pearls.RTM. 1400, Black Pearls.RTM. 1300, Black
Pearls.RTM. 1100, Black Pearls.RTM. 1000, Black Pearls.RTM. 900,
Black Pearls.RTM. 880, Black Pearls.RTM. 800, Black Pearls.RTM.
700, Black Pearls.RTM. L, Elftex.RTM. 8, Monarch.RTM. 1400,
Monarch.RTM. 1300, Monarch.RTM. 1100, Monarch.RTM. 1000,
Monarch.RTM. 900, Monarch.RTM. 880, Monarch.RTM. 800, Monarch.RTM.
700, Mogul.RTM. L, Regal.RTM. 330, Regal.RTM. 400, Vulcan.RTM. P.
Other carbon blacks include, but are not limited to, Printex 40,
Printex 80, Printex 300, Printex L, Printex U, Printex V, Special
Black 4, Special Black 5, FW1, FW2, FW18, and FW200, which are
available from Degussa Corporation (Ridgefield, N.J.); Raven 780,
Raven 890, Raven 1020, Raven 1040, Raven 1255, Raven 1500, Raven
5000, Raven 5250, which are available from Colombian Chemical
Corporation (Atlanta, Ga.); and MA100 and MA440, which are
available from Mitsubishi Chemical Corporation (Tokyo, Japan).
[0018] Suitable classes of colored pigments include, but are not
limited to, anthraquinones, phthalocyanine blues, phthalocyanine
greens, diazos, monoazos, pyranthrones, perylenes, heterocyclic
yellows, quinacridones, and (thio)indigoids. Examples of
phthalocyanine blues include copper phthalocyanine blue and
derivatives thereof (Pigment Blue 15). Examples of quinacridones
include Pigment Orange 48, Pigment Orange 49, Pigment Red 122,
Pigment Red 192, Pigment Red 202, Pigment Red 206, Pigment Red 207,
Pigment Red 209, Pigment Violet 19 and Pigment Violet 42. Examples
of anthraquinones include Pigment Red 43, Pigment Red 194 (Perinone
Red), Pigment Red 216 (Brominated Pyranthrone Red) and Pigment Red
226 (Pyranthrone Red). Examples of perylenes include Pigment Red
123 (Vermillion), Pigment Red 149 (Scarlet), Pigment Red 179
(Maroon), Pigment Red 190 (Red), Pigment Violet 19, Pigment Red 189
(Yellow Shade Red) and Pigment Red 224. Examples of thioindigoids
include Pigment Red 86, Pigment Red 87, Pigment Red 88, Pigment Red
181, Pigment Red 198, Pigment Violet 36, and Pigment Violet 38.
Examples of heterocyclic yellows include Pigment Yellow 1, Pigment
Yellow 3, Pigment Yellow 12, Pigment Yellow 13, Pigment Yellow 14,
Pigment Yellow 17, Pigment Yellow 65, Pigment Yellow 73, Pigment
Yellow 74, Pigment Yellow 93, Pigment Yellow 151, Pigment Yellow
154, Pigment Yellow 155, Pigment Yellow 117, Pigment Yellow 128,
Pigment Yellow 138, Pigment Yellow 109, Pigment Yellow 110, and
Pigment Yellow 213. These pigments are commercially available in
either powder or press cake form from a number of sources
including, BASF Corp. (Mount Olive, N.J.), Engelhard Corp. (Iselin,
N.J.), CIBA Corp. (Tarrytown, N.Y.), Clariant Corp. (Coventry,
R.I.), or Sun Chemical Corp. (Cincinnati, Ohio).
[0019] The pigment may also include the Hostafine.RTM. series of
pigments, such as Hostafine.RTM. Yellow GR, Hostafine.RTM. Yellow,
Hostafine.RTM. Red FRLL, Hostafine.RTM. Rubine F6B, Hostafine.RTM.
Blue 2G, Hostafine.RTM. Black T, and Hostafine.RTM. Black TS, which
are available from Clariant GmbH (Muttenz, Switzerland); Normandy
Magenta RD-2400 (Paul Uhlich), Paliogen Violet 5100 BASF Corp.),
Paliogen.RTM. Violet 5890 (BASF Corp.), Permanent Violet VT2645
(Paul Uhlich), Heliogen Green L8730 (BASF Corp.), Argyle Green
XP-111-S (Paul Uhlich), Brilliant Green Toner GR 0991 (Paul
Uhlich), Heliogen.RTM. Blue L6900, L7020 (BASF Corp.),
Heliogen.RTM. Blue D6840, D7080 (BASF Corp.), Sudan Blue OS (BASF
Corp.), PV Fast Blue B2GO1 (American Clariant), Irgalite Blue BCA
(Ciba), Paliogen.RTM. Blue 6470 (BASF Corp.), Sudan III (Matheson,
Coleman, Bell), Sudan II (Matheson, Coleman, Bell), Sudan IV
(Matheson, Coleman, Bell), Sudan Orange G (Aldrich), Sudan Orange
220 (BASF Corp.), Paliogen.RTM. Orange 3040 (BASF Corp.), Ortho
Orange OR 2673 (Paul Uhlich), Paliogen.RTM. Yellow 152, 1560 (BASF
Corp.), Lithol Fast Yellow 0991K (BASF Corp.), Paliotol Yellow 1840
(BASF Corp.), Novoperm.RTM. Red BN (Clariant), Novoperm.RTM. Yellow
FG 1 (Clariant), Permanent Yellow YE 0305 (Paul Uhlich), Lumogen
Yellow D0790 (BASF Corp.), Suco-Gelb L1250 (BASF Corp.),
Suco-Yellow D1355 (BASF Corp.), Hostaperm.RTM. Pink E (American
Clariant), Fanal Pink D4830 (BASF Corp.), Cinquasia Magenta
(DuPont), Lithol Scarlet D3700 (BASF Corp.), Toluidine Red
(Aldrich), Scarlet for Thermoplast NSD PS PA (Ugine Kuhlmann of
Canada), E. D. Toluidine Red (Aldrich), Lithol Rubine Toner (Paul
Uhlich), Lithol Scarlet 4440 (BASF Corp.), Bon Red C (Dominion
Color Company), Royal Brilliant Red RD-8192 (Paul Uhlich), Oracet
Pink RF (Ciba), Paliogen.RTM. Red 3871K (BASF Corp.), Paliogen.RTM.
Red 3340 (BASF), and Lithol Fast Scarlet L4300 (BASF Corp.).
[0020] The polymer attached to the pigment may be formulated so
that at least a first portion of the polymer is soluble in the ink
vehicle and at least a second portion of the polymer is insoluble
in the ink vehicle. The polymer 2 may be a random polymer or a
block polymer and may include at least one hydrophobic segment 4
and at least one hydrophilic segment 6, as shown in FIGS. 1 and 2.
The hydrophobic segment 4 may be attached to the pigment 8 and the
hydrophilic segment 6 may be attached to the hydrophobic segment 4,
as shown in FIG. 1. As such, the hydrophobic segment 4 may be
closer than the hydrophilic segment 6 to the surface of the pigment
8 when the polymer 2 is in the elongated or extended configuration.
For the sake of simplicity, two polymers 2 are shown attached to
the pigment 8 in FIG. 1. However, it is understood that numerous
polymers 2 may be attached to the pigment 8 to form the
polymer-attached pigment 10. Alternatively, the hydrophilic segment
6 may be attached to the pigment 8 and the hydrophobic segment 4
may be attached to the hydrophilic segment 6, as shown in FIG. 2.
The polymer 2 may also include more than two portions with each
portion of the polymer 2 being either soluble or insoluble in the
ink vehicle. For instance, a triblock copolymer 2 having one
hydrophobic segment 4 and two hydrophilic segments 6 is shown in
FIG. 3. The polymer 2 may also be formed from multiple blocks or
segments that each includes hydrophobic monomers, hydrophilic
monomers, or mixtures thereof. For instance, a hydrophobic block,
formed from hydrophobic segments 4, may be attached to the pigment
8. A block having a mixture of hydrophobic segments 4 and
hydrophilic segments 6 may be attached to the hydrophobic block.
Similarly, a hydrophilic block, formed from hydrophilic segments 6,
may be attached to the pigment 8. A block having a mixture of
hydrophobic segments 4 and hydrophilic segments 6 may be attached
to the hydrophilic block. The hydrophobic segments 4 and the
hydrophilic segments 6 may be polymerized by conventional
techniques to form the polymer 2.
[0021] Alternatively, the pigment 8 may have a plurality of
different types of polymers 2 attached to its surface. For
instance, the pigment 8 may include both hydrophobic polymers and
hydrophilic polymers attached to its surface.
[0022] The hydrophobic segment 4 that may be used in the polymer 2
includes, but is not limited to, a styrene, an alkyl styrene, a
phenoxyethylacrylate, an alkyl or aryl acrylate, an alkyl or aryl
methacrylate, and a benzylmethacrylate. The hydrophilic segment 6
may include, but is not limited to, an acrylic acid, a methacrylic
acid, an acrylamide, styrene-4-sulfonic acid, 4-vinylbenzoic acid,
and alkylene oxide adducts of acrylic acid or methacrylic acid,
such as hydroxyethylacrylate, hydroxyethylmethacrylate, or ethyl
triethyleneglycol acrylate. The hydrophilic segment 6 may be an
acid having a pK.sub.a of less than approximately 5, such as a
sulfonate or phosphate adduct of acrylic acid or methacrylic acid.
The hydrophilic segment may be cationic, such as
dimethylaminoethylacrylate or its quaternized forms. Nonionic,
anionic, or cationic functional groups may be present on the
polymer 2 simultaneously, either within a polymer 2 or on separate
polymers 2 attached to the same pigment. The hydrophobic segment 4
and the hydrophilic segment 6 may be present at varying ratios, as
long as the amounts of the hydrophobic segment 4 and the
hydrophilic segment 6 provide colloidal stability to the pigment
dispersion.
[0023] The pigment 8 may include multiple sites on its surface to
which the polymer 2 may attach. The polymer 2 may bond to some or
all of the attachment sites to provide a desired degree of
modification of the pigment 8. As shown in FIG. 1, the polymer 2
may be attached to the surface of the pigment 8 at one attachment
site or may have multiple attachment sites to the pigment surface.
The polymer-attached pigment 10 may include one type of polymer 2
attached to the pigment 8 or may include different types of
polymers attached to the pigment 8. The polymer 2 may have a
molecular weight ranging from approximately 1500 to less than
approximately 50,000.
[0024] The polymer 2 may be chemically bonded to the pigment 8. In
one particular embodiment, the polymer 2 is covalently bonded to
the pigment 8. The polymer 2 may be attached to the pigment 8 using
conventional techniques, such as by using a diazonium reaction. The
polymer 2 may be formed by polymerizing the hydrophobic segment 4
and the hydrophilic segment 6. A diazonium salt of the polymer 2
may then be formed by conventional techniques and the polymer 2
reacted with the pigment 8 to form the polymer-attached pigment 10.
Alternatively, a diazonium reaction may be used to covalently bond
the hydrophobic segment 4 to the pigment 8. A Diels-Alder
cycloaddition reaction may also be used to attach functional groups
to surfaces of the pigment 8. Disulfide chemistry or thionyl
chloride chemistry may also be used to attach functional groups to
the surface of the pigment 8. The hydrophilic segment 6 may then be
bonded to the hydrophobic segment 4 by a reaction that form is a
covalent bond between the hydrophilic segment 6 and the hydrophobic
segment 4, such as an S.sub.N2 displacement reaction, a 1,2- or
1,4-addition reaction, a condensation reaction, an acylation
reaction, or a ring-forming reaction.
[0025] A sufficient amount of the polymer 2 may be attached to the
pigment 8 to disperse the polymer-attached pigment 10 in the ink
vehicle. The pigment 8 may have from approximately 10% to
approximately 70% of its surface area bound with the polymer 2. In
one particular embodiment, from approximately 50% to approximately
70% of the surface area of the pigment 8 is bound with the polymer
2.
[0026] The polymer-attached pigment 10 may be present in the inkjet
ink in an amount that provides a desired color, hue, and saturation
when the polymer-attached pigment 10 is precipitated on a print
medium, such as during printing. For instance, the polymer-attached
pigment 10 may be present in the inkjet ink from approximately
0.25% by weight ("wt %") to approximately 15 wt % of a total weight
of the inkjet ink. In one particular embodiment, the
polymer-attached pigment 10 is present from approximately 1 wt % to
approximately 10 wt % of the total weight of the inkjet ink.
[0027] The inkjet ink may also include the ink vehicle, which is a
mixture of water and at least one water-soluble or water-miscible
organic solvent. The inkjet ink may include from approximately 20
wt % to approximately 95 wt % of water based on the total weight of
the inkjet ink. In one particular embodiment, the inkjet ink
includes from approximately 70 wt % to approximately 95 wt % of
water based on the total weight of the inkjet ink. The organic
solvent may be present from approximately 0.5 wt % to approximately
25 wt % of the total weight of the inkjet ink.
[0028] The organic solvent may include, but is not limited to,
1,2-hexanediol; a polyhydric alcohol, such as ethylene glycol,
diethylene glycol, triethylene glycol, polyethylene glycol,
propylene glycol, polypropylene glycol, and glycerol; a polyhydric
alcohol ether, such as ethylene glycol monomethyl ether, ethylene
glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene
glycol monoethyl ether, diethylene glycol monobutyl ether, and
ethylene glycol monophenyl ether; and a nitrogen-containing
solvent, such as N-methyl-2-pyrrolidinone, 2-pyrrolidinone (2-P), a
substituted pyrrolidinone, and triethanolamine. Monohydric
alcohols, such as methanol, ethanol, and isopropyl alcohol may also
be used in the inkjet ink. In one particular embodiment, the
organic solvent in which the second portion of the polymer 2 is
soluble has a higher boiling point than the boiling point of
water.
[0029] At least one of the organic solvents in the inkjet ink may
be an organic solvent in which at least a portion of the polymer 2
is poorly soluble. The organic solvent may include
nitrogen-containing compounds, such as 2-pyrrolidone (2-P),
N-methyl-pyrrolidinone (NMP), 1,3-dimethylimidazolid-2-one, and
octyl-pyrrolidone; diols, such as ethanediols (e.g.,
1,2-ethanediol), propanediols (e.g., 1,2-propanediol,
1,3-propanediol, 2-ethyl-2-hydroxymethyl-1,3-propanediol,
ethylhydroxy-propanediol), butane-diols (e.g., 1,2-butanediol,
1,3-butanediol, 1,4-butanediol), pentanediols (e.g.
1,2-pentanediol, 1,5-pentanediol), hexanediols (e.g.,
1,2-hexanediol, 1,6-hexanediol, 2,5-hexanediol), heptanediols
(e.g., 1,2-heptanediol, 1,7-heptanediol), octanediols (e.g.,
1,2-octanediol, 1,8-octanediol); alcohols, such as C.sub.3-C.sub.6
alcohols (e.g., propanol, butanol, pentanol, and hexanol),
including isomers thereof (e.g., 1-propanol and 2-propanol); glycol
ethers and thioglycol ethers commonly employed in ink-jet inks,
such as polyalkylene glycols such as polyethylene glycols (e.g.,
diethylene glycol (DEG), triethylene glycol, tetraethylene glycol),
propylene glycols (e.g., dipropylene glycol, tripropylene glycol,
tetrapropylene glycol); polymeric glycols (e.g., PEG 200, PEG 300,
PEG 400, PPG 400); thiodiglycol; and mixtures thereof. Additional
organic solvents include hydantoins (glycol ureas) and derivatives
thereof, such as a hydantoin containing ethyl hydroxide and methyl
groups, available from Lonza, Inc. as Dantocol DHE, and
polyalkoxylated triols, such as Multranol 4012, which is a
polyalkoxylated triol having a molecular weight of about 440,
available from Bayer.
[0030] The organic solvent may be selected based on its solubility
parameter, which is a convenient method of describing the organic
solvent or mixtures of organic solvents that may be used in the
present invention. Solubility parameters, such as the Hansen
solubility parameters, are known to those of skill in the art. The
Hansen solubility parameters are a three-parameter system that
divides a total Hildebrand value into three parts: a dispersion
force component a hydrogen bonding component, and a polar component
according to the following formula:
.delta..sub.t.sup.2=.delta..sub.d.sup.2+.delta..sub.p.sup.2+.delta..sub.n-
.sup.2 where .delta..sub.t.sup.2 is the Total Hildebrand parameter,
.delta..sub.d.sup.2 is the dispersion component,
.delta..sub.p.sup.2 is the polar component, and .delta..sub.h.sup.2
is the hydrogen bonding component. The Hansen solubility parameters
are thus additive. By using the Hansen solubility parameter,
organic solvents may be divided into weak, moderate, or strong
hydrogen bonders. The organic solvent or mixture of organic
solvents used in the inkjet ink may be a moderate or a strong
hydrogen bonder. Out of the moderate hydrogen bonders, organic
solvents and mixtures of organic solvents having a
.delta..sub.t.sup.2 value ranging from approximately 10 to
approximately 12 are preferred, such as ketones, esters, ethers, or
glycol monoethers, but excluding water. Out of the strong hydrogen
bonders, organic solvents and mixtures of organic solvents having a
.delta..sub.t.sup.2 value ranging from approximately 11.5 to
approximately 13.5 are especially preferred, such as alcohols,
polyols, amines, acids, and amides. In one particular embodiment,
the organic solvent is 1,2-hexanediol, ethylene glycol monophenyl
ether, or mixtures thereof.
[0031] To further improve gloss and durability, the inkjet ink may
optionally include at least one binder. If present in the inkjet
ink, the binder may interact with the polymer 2 of the
polymer-attached pigment 10. The binder may be formulated so that
at least a first portion of the binder is soluble in the ink
vehicle of the inkjet ink and at least a second portion of the
binder is insoluble in the ink vehicle of the inkjet ink. The
binder may interact with the polymer 2 of the polymer-attached
pigment 10 by formulating the binder to exhibit a compact
configuration in the aqueous environment and an elongated
configuration in the organic-enriched environment.
[0032] The binder may be a random polymer or a block polymer having
a central hydrophobic portion and two adjacent hydrophilic
portions. As shown in FIG. 7, the binder 12 may be a triblock
copolymer that includes a hydrophobic segment 14 and two
hydrophilic segments 16, 16' adjacent to each end of the
hydrophobic segment 14. The hydrophobic segment 14 of the binder 12
may be selected from the list of hydrophobic segments 4 disclosed
herein for use in the polymer 2 of the polymer-attached pigment 10.
Each of the hydrophilic monomers that are used in the hydrophilic
segments 16, 16' of the binder 12 may be independently selected
from the list of hydrophilic segments 6 disclosed herein for use in
the polymer 2 of the polymer-attached pigment 10. As such, each of
the hydrophilic segments 16, 16' may be the same or different. The
binder 12 may also include more than three portions with each
portion of the binder 12 being either soluble or insoluble in the
ink vehicle. The hydrophobic segment 14 and the hydrophilic
segments 16, 16' may be polymerized by conventional techniques to
form the binder 12. The binder 12 may be present in the inkjet ink
in a range of from approximately 2 wt % to approximately 4 wt
%.
[0033] Depending on the desired properties of the inkjet ink, the
ink vehicle may optionally include additives or ingredients that
are known in the art, such as surfactants, dispersants, pH
adjusters, buffers, humectants, antioxidants, solubilizers,
ultraviolet absorbers, anti-corrosion additives, anti-kogation
additives, or biocides. For instance, the inkjet ink may optionally
include a glycerin-modified short chain ethylene oxide dispersant,
such as LEG-1, which is available from Lipo Chemical Co. (Paterson,
N.J.).
[0034] The inkjet ink may be produced by dispersing the
polymer-attached pigment 10 in the ink vehicle. The
polymer-attached pigment 10 may be substantially homogenously
dispersed in the inkjet ink using conventional techniques, such as
ultrasonic energy or a media mill. The polymer-attached pigment 10
may be dispersed without using conventional dispersants. Any
additional ingredients may be mixed and dissolved into the pigment
dispersion using conventional techniques, such as by using a ball
mill, a sand mill, a roll mix, an agitator mill, a Henschel mixer,
a colloid mill, or an ultrasonic homogenizer. If the binder 12 is
present in the inkjet ink, the binder 12 may be mixed and dissolved
into the pigment dispersion using conventional techniques.
[0035] The inkjet ink of the present invention may be used in an
inkjet printing process, such as a thermal, piezoelectric,
drop-on-demand, or continuous inkjet printing process. To produce
the printed image, the inkjet ink may be deposited on the print
medium by conventional inkjet printing techniques, which are not
described in detail herein. The print medium may be a conventional
print medium known in the art, such as a plain or coated paper, an
ink-jet photo-type paper, or an uncoated, substantially or
completely nonporous media, such as billboard paper, vinyl, or
PET.
[0036] Particles of the polymer-attached pigment 10 may have a
variable particle size depending on an environment to which they
are exposed. The dispersed pigment particles may have a small
particle size in a substantially aqueous environment and a large
particle size in an environment having a high organic solvent
content, referred to herein as the "organic-enriched environment."
The dispersed pigment particles may also provide a variable
viscosity to the inkjet ink depending on the environment in which
the polymer-attached pigment 10 is dispersed. If the environment is
substantially aqueous, the dispersed pigment particles may provide
a low viscosity to the inkjet ink. However, if the environment is
enriched in organic solvents, the inkjet ink may have an increased
viscosity.
[0037] The hydrophobic segment 4 and the hydrophilic segment 6 of
the polymer 2 may provide the variable particle size to the
polymer-attached pigment 10 and the corresponding variable
viscosity. When the polymer-attached pigment 10 is in the aqueous
environment, the polymer 2 may be in the compact configuration, as
shown in FIGS. 1-3. Since the hydrophobic segment 4 is poorly
soluble in the aqueous environment, the hydrophobic segment 4 may
be collapsed on the surface of the pigment 8, as shown in FIG. 1.
If the hydrophilic segment 6 is directly attached to the pigment 8,
the hydrophobic segment 4 may be collapsed back onto the surface of
the pigment 8, as shown in FIGS. 2 and 3. As such, the particle
size of the polymer-attached pigment 10 may be small and compact.
Since the polymer-attached pigment 10 is in the compact
configuration when it is present in the inkjet ink formulation, the
viscosity of the inkjet ink is reduced.
[0038] The polymer-attached pigment 10 may have an average particle
size ranging from approximately 1 nm to approximately 300 nm in the
aqueous environment. In one particular embodiment, the particle
size of the polymer-attached pigment 10 is less than approximately
150 nm. The polymer 2 may exhibit the compact configuration when
the polymer-attached pigment 10 is present in the aqueous based ink
vehicle of the inkjet ink. The small particle size of the
polymer-attached pigment 10 may provide a corresponding low
viscosity to the inkjet ink. The viscosity of the inkjet ink may
range from approximately 1 centipoise ("cP") to approximately 15
cP. This low viscosity may be obtained even though the amount of
polymer 2 in the inkjet ink is effectively increased relative to
the amount of dispersant in a conventional inkjet ink.
[0039] When the polymer-attached pigment 10 is in the
organic-enriched environment, the polymer 2 may exhibit the
elongated configuration shown in FIGS. 4-6. The organic-enriched
environment may include an environment in which the concentration
of the organic solvent in the ink vehicle has increased or a
portion of the water in the ink vehicle has been removed. For
instance, when the inkjet ink is deposited on the print medium to
produce the printed image, the water in the ink vehicle may
evaporate, producing the organic-enriched environment. As the water
evaporates, the concentration of the organic solvent in the ink
vehicle increases. For sake of example only, as the inkjet ink
dries, the ink vehicle may include from approximately 50 wt % to
approximately 90 wt % of the organic solvent, rather than from
approximately 80 wt % to approximately 90 wt % water. As the
concentration of the organic solvent increases, the hydrophobic
segment 4 may become soluble in the organic-enriched environment of
the ink vehicle, as shown in FIGS. 4-6. Therefore, the hydrophobic
segment 4 may extend away from the surface of the pigment 8 and
increase the particle size of the polymer-attached pigment 10. When
the polymer 2 is in the elongated configuration, the particle size
of the polymer-attached pigment 10 may increase by an amount
ranging from approximately 5% to approximately 25%.
[0040] For instance, a radius of the pigment 8 may increase by up
to approximately 100 Angstroms ("{acute over (.ANG.)}") when the
polymer-attached pigment 10 is in the organic-enriched environment.
For sake of example only, if the diameter of the pigment 8 is 10
nm, the particle size of the polymer-attached pigment 10 may
increase in the organic enriched environment by up to approximately
100 {acute over (.ANG.)}, increasing the particle size of the
polymer-attached pigment 10 to approximately 30 nm. Similarly, if
the diameter of the pigment 8 is 300 nm, the particle size of the
polymer attached pigment 10 may increase in the organic-enriched
environment by up to approximately 100 {acute over (.ANG.)},
increasing the particle size of the polymer-attached pigment 10 to
approximately 320 nm.
[0041] When the polymers 2 are elongated or extended, the polymers
2 attached to adjacent polymer-attached pigments 10 may become
entangled and form a film over the printed image. Therefore, the
printed image produced using the inkjet ink of the present
invention may exhibit improved gloss and durability, such as
improved resistance to smear, smudge, highlighter smudge, gasfade,
or airfade.
[0042] The polymer 2 may also be configured to adopt the elongated
configuration upon a change in temperature or pH. The temperature
or pH change may alter the solubility of the polymer 2, causing the
polymer 2 to extend into the elongated configuration. In this
embodiment, the polymer 2 may include hydrophobic and hydrophilic
segments 4,6 that exhibit conformation changes upon changes in
temperature or pH. These types of polymers are known in the art and
are not discussed in detail herein.
[0043] The binder 12 may also exhibit a variable configuration
depending on the environment to which the binder 12 is exposed.
When the binder 12 is in the aqueous environment, the hydrophobic
segment 14 may be curled up on itself, as shown in FIG. 7, because
the hydrophobic segment 14 is poorly soluble in the aqueous
environment. Therefore, the binder 12 may be in the compact
configuration when the binder 12 is exposed to the aqueous
environment, such as when the binder 12 is present in the inkjet
ink formulation. When the binder 12 is exposed to the
organic-enriched environment, such as when the inkjet ink is
applied to the print medium and the water evaporates, the
hydrophobic segment 14 may extend, as shown in FIG. 8, since the
hydrophobic segment 14 is more soluble in the organic-enriched
environment. As such, the binder 12 may be in the elongated
configuration when the binder 12 is exposed to the organic-enriched
environment. In the elongated configuration, the hydrophilic
segments 16, 16' may repel the organic-enriched environment. By
doing so, the hydrophilic segments 16, 16' may have increased
interactions with the hydrophilic segments 16, 16' on other binders
12 in the inkjet ink or with the hydrophilic segment 6 on the
pigment-attached polymer 10. These interactions between the binders
12 and between the binder 12 and the polymer 2 may cause the
binders 12 and the polymer 2 to become entangled. As such, the
binder 12 may contribute to the film formed over the printed image.
Therefore, the printed image produced by the inkjet ink of the
present invention may exhibit improved gloss and durability, such
as improved resistance to smear, smudge, highlighter smudge,
gasfade, or airfade.
[0044] Since the binder 12 is designed and tailored to interact
with the polymer 2, interactions between the binder 12 and the
polymer 2 may be statistically increased. Therefore, smaller
amounts of the binder 12 may be used in the inkjet ink to achieve
the desired improvement in gloss and durability.
[0045] In addition to interacting with the polymer-attached
pigments 10 as described herein, the binder 12 may interact with
conventional pigment dispersions. As such, the binder 12 may
provide improved gloss and durability when used in inkjet inks that
includes conventional pigment dispersions.
[0046] The following examples describe representative compositions
of inkjet inks of the present invention that include the
polymer-attached pigment 10. The examples are merely illustrative
and are not meant to limit the scope of the present invention in
any way.
EXAMPLES
Example 1
Inkjet Ink Compositions
[0047] Inkjet formulations including a polymer-attached pigment and
organic solvents in which a portion of the polymer is soluble are
prepared. The polymer and the organic solvents that are used in
each of the inkjet formulations are shown in Table 1. The polymer
is attached to carbon black as the pigment. The polymer is attached
to a surface of the pigment by conventional techniques. The inkjet
inks are formulated by conventional techniques. TABLE-US-00001
TABLE 1 Formulations of Inkjet Inks. Molecular weight Acid No. of
Formulation Polymer (monomer/monomer) of Polymer Polymer Organic
solvents 1 styrene/acrylic acid 6000 170 5% 2-P, 4% 1,2-hexanediol,
3% DEG, 3% LEG-1 2 styrene/methacrylic acid 10000 160 5% 2-P, 5%
1,2-hexanediol, 2% Dowanol EPh, 3% LEG-1 3 styrene/phenoxyethyl-
15000 180 4% 2-P, 5% 1,2-hexanediol, acrylate/methacrylic acid 3%
Dowanol EPh, 3% LEG-1 4 benzylmethacrylate/ 15000 140 5% 2-P, 5%
1,2-hexanediol, methacrylic acid 5% tetraethylene glycol, 3% LEG-1
5 styrene/methoxy 12000/4000 5% 2-P, 5% 1,2-hexanediol,
polyethylene glycol 5% tetraethylene glycol, (550) methacrylate 3%
LEG-1 6 benzylmethacrylate/methoxy 20000 70 5% 2-P, 5%
1,2-hexanediol, polyethylene glycol (550) 5% tetraethylene glycol,
methacrylate/methacrylic acid 3% LEG-1 7
styrene/methylmethacrylate/ 10000 150 5% 2-P, 5% 1,2-hexanediol,
acrylic acid 3% ethylene glycol, 3% LEG-1 8
styrene/butylacrylate/methacrylic acid; 10000 150 8%
1,2-hexanediol, styrene:butylacrylate = 2:1 3% 2-P, 3% LEG-1
Example 2
Production of Printed Image
[0048] A test plot is printed on a print medium using a
Hewlett-Packard Deskjet 970 inkjet printer and the inkjet inks
described in Example 1. The printed images will exhibit improved
gloss and improved resistance to smear, smudge, highlighter smudge,
and gasfade or airfade compared to an image printed with an inkjet
ink including a conventional self-dispersed pigment.
* * * * *